1. Field of the Invention
This invention relates to a device for driving the ring levers controlling the keys of a high-speed rotary dobby which, by using rocker arms pivoted on said ring levers symmetrically about an axis of symmetry passing through the fulcrum of said levers and made suitably rigid by pairs of electromagnetic systems with one of two dragging grooves rocking in mutual opposition symmetrically about said axis of symmetry, results in considerable compactness, efficiency and constructional simplicity, allows the operating speed to be increased, and enables the dobby to be halted and put into reverse running at any moment, as all idle times are eliminated.
2. Description of the Related Art
As already known from our previous European Patent Appln. publication No. 0 466 234 of Jan. 15, 1992, the device for driving the ring levers controlling the keys of a high-speed rotary dobby comprises, for each lever, a V-shaped spring which has the ends of its two arms inserted into a cavity of said lever facing the lever fulcrum. The spring being mounted preloaded between two fixed shoulders positioned symmetrically about the axis of symmetry of said spring, which passes through said fulcrum of the controlling ring lever. This lever also comprises a second cavity opposite the preceding and cooperating with a slide to which there is hinged the lower end of a sector which rocks symmetrically about said axis of symmetry. The sector comprising in its upper part two valleys arranged symmetrically about said axis of symmetry and cooperating with the lower end of an overlying pusher rod. The pusher rod is hinged at its upper end to an arm projecting from a single dobby shaft made to rock by a control mechanism preferably of cam type synchronized with the dobby modulation mechanism. The pusher rod is slidingly inserted between two pins of a needle selector which cooperates with the port of a programmer by the action of a thrust spring and a return extractor comb to rock by a second control mechanism preferably of cam type and also synchronized with said modulation mechanism.
Such a known device, besides being of evident constructional complexity, has the drawback of a loss of operational effectiveness and reliability with time because of the presence of said V-shaped spring, and in particular presents idle times during which the dobby cannot be put into reverse running and which considerably limit its operational speed. In this respect, in said known device the programmer provides the enabling command to the selector needle, which can then move to cause the forcing member (pusher rod) to operate and transmit the desired movement to the controlling ring lever via the rocking sector; the needle and the rocking sector must then be returned to their rest position with the aid respectively of a further control mechanism and said V-shaped spring to be able to recommence the entire cycle from the beginning, hence the entire time required for these operations which decide whether the ring lever is to be moved represents time lost to the dobby.